The present invention relates to pressed paperboard forming machines, and particularly to pressed paper cut-in-place dies for forming paper containers and the like.
Most of the pressed paperboard forming machines currently in production consist of one of three processes. In the first, the paperboard blank is precut on a separate machine and the stack of blanks are then placed into a hopper on the forming machine whereby they are then fed one at a time into a forming section. In the forming section, the blank is docked against physical stops which centers the blank over matched, metal male and female die halves. The top die which is usually the male die then descends engaging the paper and forcing it into the female cavity. The male die presses the paperboard against the female die for a period of time, then begins to ascend to an open position. An ejector mechanism in the female die lifts the container out of the female die and because the female die is on an acute angle, the container falls out of the die and press onto a conveyor. In some machines in the past, the dies have been arranged to form the paper plate or container upside down.
In the second system, a web of paperboard is unwound from a a roll and fed into a press comprised of three sections; a feed or metering section, a cutting or blanking section, and a forming section. In this type system, the feed section meters the paperboard into the cutting section over a female cavity or hole. The top platen which contains male punches that match the size of the female cavity or hole in the bottom then descends and shears the paperboard blanks from the web. The blanks then drop through the hole and are transferred to the forming section by sliding via gravity on rails set to 45xc2x0 angles. In the forming section, the blank is docked against physical stops which centers the blank over matched, metal male and female die halves. The top die which is usually the male die then descends engaging the paper and forcing it into the female cavity. The male die presses the paperboard against the female die for a period of time, then begins to ascend to an open position. An ejector mechanism in the female die lifts the container out of the female die and because the female die is on a 45xc2x0 angle, the container falls out of the die and press onto a conveyor.
The third system consists of feeding a web of paperboard into a cutting section that utilizes a steel rule die to cut and crease the blanks simultaneously. Although the blanks have been cut from the web, they are still attached to the web by small nicks in the paperboard. The paper is then indexed with the blank intact until it exits the cutting section. As the web with the pre-cut blank exits the cutting section, a set of rollers picks up the blank and strips it from the web. The scrap exits the bottom of the machine and is cut into pieces as the blank is urged by the rollers into the forming die section. In the forming section, the blank is docked against physical stops which centers the blank over matched, metal male and female die halves. The top die which is usually the female die then descends engaging the paper and forcing it around the male die. The female die presses the paperboard against the male die for a period of time, then begins to ascend to an open position. As the press begins to open, the draw ring surrounding the male die follows the press upward stripping the part from the male die. When the part has been lifted to the point of clearing the male die, the draw ring is restrained from further travel and the part is blown off the ring and onto a conveyor by strategically placed air jets.
According to the present invention, a die system for cutting a piece of sheet stock to create a blank and forming the blank to create a container includes first and second mating die halves and a cutting punch. The first and second die halves are configured to move together to form the container from the blank. The cutting punch extends about the first die half and is movable therewith. The cutting punch is configured to cut the piece of sheet stock to create the blank. Movement of the die halves together causes the cutting punch to cut the blank from the piece of sheet stock and further movement of the die halves together causes the first and second die halves to form the container from the blank.
In preferred embodiments, the first die half is a female die half and the second die half is a male die half. The female and male die halves are positioned substantially horizontally with the female die half being positioned vertically above the male die half. The male die half is stationary so that the female die half moves vertically downwardly to mate with the male die half to form the container and vertically away from the male die half to release the container from between the female and male die halves.
The die system may also include a draw ring extending about the male die half. The draw ring is movable with the female die half relative to the male die half so that the blank is held between the draw ring and a perimetal surface of the first die half as the container is being formed. The die system may also include a stripper ring extending about the cutting punch and movable with the first die half. The stripper ring is configured to hold the piece of sheet stock in place as the sheet stock is being cut and the blank is being formed. The die system may also include a cutting ring extending about and spaced-apart from the second die half and positioned to lie opposite the stripper ring. The cutting ring is configured to cooperate with the stripper ring to hold the sheet stock between the stripper ring and the cutting ring. The cutting ring is also configured to allow the cutting punch to extend between the second die half and the cutting ring to cut the sheet stock.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of illustrated embodiments exemplifying the best mode of carrying out the invention as presently perceived.